The origin and evolution
of culture and creativity
On- Creativity |
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1.1 Components of an Evolutionary System In order for evolution to happen there must be: |
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In biological evolution, the evolving patterns of information are genes encoded as sequences of nucleotides. Variations arise through mutation and recombination, and natural selection weeds out those that are maladaptive. Replication takes place at the level of the genotype. In cultural evolution, the evolving patterns of information are memes - mental representations of ideas, behaviors, or other theoretical or imagined constructs, perhaps encoded as patterns of neuron activation. Variations are created by combining, transforming, and reorganizing representations, consciously or unconsciously, or through errors in transmission. Replication is phenotypically mediated; it occurs when representations are transformed into action or language, transmitted through processes such as imitation, and reproduced, more or less, in another brain. Incorporation of these new information patterns into the society alters the selective pressures and constraints exerted by the social environment, which in turn leads to the generation of yet more patterns. Thus memes, like DNA, comprise a self-sustained system for the relentless exploration and transformation of a space of possible patterns. |
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Figure 1: Schematic distribution of Hamming distances between addresses of meme X and addresses of storage locationsA computer reads from memory by simply looking at the address in the address register and retrieving the item at the location specified by that address. The sparseness of the SDM prohibits this kind of one-to-one correspondence, but it has two tricks up its sleeve for getting around this problem. First, it feigns content addressability, as follows. The particular pattern of 1s and 0s that constitutes a meme causes some of the synapses leading out from the focus to be excited and others to be inhibited. The locations where memes get stored are memory neurons, and the address of a neuron amounts to the pattern of excitatory and inhibitory synapses from focus to memory that make that neuron fire. Activation of a memory neuron causes the meme to get written into it. Thus there is a systematic relationship between the memes' information content and the locations they activate. Second, since the probability that the ideal address for storing a meme corresponds to an actual location in memory is vanishingly small, storage of the meme is distributed across those locations whose addresses lie within a sphere (or more accurately, hypersphere) of possible addresses surrounding the ideal address (figure 2). The radius (in Hamming metric) of this sphere is determined by the neuron activation threshold. Each location participates in the storage of many memes. In this example we assume that 10,000 memes have been stored in memory. Each meme is stored in 1,000 (of the 1,000,000 possible) locations, so there are approximately 10 memes per location. The storage process works by updating each of the L counters in each location; to store a 1 the counter is incremented by 1, and to store a 0 it is decremented by 1. These nearly one million operations occur in parallel. |
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Figure 2: Meme X is stored in all locations within hypersphere of radius k surrounding its ideal address If after a meme, say meme X, is stored, the individual's attention is directed toward external stimuli, then nothing is retrieved from memory. But to the extent that memory contributes to the next instant of awareness, the storage of X activates retrieval of not only X itself but all the other memes that have been stored in the same locations. The next meme to be encoded in the focus, , is found by determining the best match; that is, by averaging the contributions of all retrieved memes feature-by-feature. Whereas the 1,000 retrieved copies of X (and memes similar to X) reinforce one another, the roughly 10,000 other retrieved memes are statistically likely to cancel one another out, so that ends up being similar to X. Though is a reconstructed blend of many memes it can still be said to have been retrieved from memory. can now be used to address the memory, and this process can be reiterated until it converges on meme Y that satisfies a current need. This is how the SDM accomplishes depth-first search. The closer Y is to X, the faster the convergence. In our example, assuming r=425, if X and Y are more than 200 bits apart Y is unlikely to be retrieved, but if they are 170 bits apart Y will be retrieved in about four iterations. Keeler [48] has shown that SDM is a superset of Hopfield-type and connectionist models of autoassociative or heteroassociative memory. The SDM formulation is used here because it lends itself to an understanding of the mechanics of phenomena we are interested in. Since the dynamics emerges from the statistics, rather than from a central executive, it can cope with creative and seemingly unmechanical cognitive phenomena such as wordplay or slips of the tongue. Moreover it is ideally suited to handle the problem of sequential access, which will become relevant when we look at how an infant establishes a train of thought. To model the recollection of a sequence, meme X is simply used as the address to write Y, Y as the address to write Z, and so on. Working memory can be viewed as the memes that lie within a given Hamming distance of the meme in the focus such that they are retrievable within a certain number of iterations. Categorization could involve the identification of a feature pattern, and readdressing memes that contain this pattern so that their new addresses put them within working memory reach of one another. Kanerva shows that the architecture of common neural components and circuits in the brain are ideally suited to implement a SDM. In SDM, associations between memes are not explicitly represented as connection strengths but as proximity in multidimensional space. However in the end they amount to the same thing. The smaller the Hamming distance between two memes, the higher the probability that they will be retrieved simultaneously and blended together in the focus (or one after the other in a chain of related thoughts). What allows the memes to be retrieved simultaneously, however, is that they are either stored in the same neurons or in neurons with nearby addresses, which in turn reflects the neurons' connectivity. Thus factors that affect the storage of a meme will also affect retrieval of that meme; the two processes are intimately connected. |
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9 A Memetic Perspective on Induction, Censors, and the Unconscious We turn now to how the cultural evolution perspective can shed light on some aspects of how people think and interact. |
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TEXTS
References [1] Alexander, R.D. (1980) Darwinism and human affairs, Pitman. |